In general, a black pattern in lattice form called a black matrix is disposed between color pixels of a color filter in order to improve contrast. In a conventional black matrix, a method of forming a pattern by depositing and etching chrome (Cr) as a pigment in an entire glass substrate was used, but a high cost is required in a process, a problem of a high reflectivity of chrome and a problem of environmental pollution due to a chrome waste fluid occur.
Due to such a reason, a study of a black matrix using a pigment dispersion method that can perform a minute processing has been actively performed and a study of producing a black composition with a coloring pigment in addition to carbon black has been performed, but because a coloring pigment in addition to carbon black has a weak light shielding property, a combination amount thereof should be very much increased and thus a viscosity of the composition increases, whereby it is difficult to handle the composition and strength of a formed film or a close contact property with a substrate is remarkably deteriorated.
Nowadays, as a request for improving performance in a photosensitive resin composition industry, many studies for a photosensitive resin composition have been performed and for example, there are a color filter composition, to which a binder is applied, which is newly developed for improving sensitivity, a black matrix resin composition having improved sensitivity by using a high sensitivity photopolymerization initiator, and a black matrix resin composition having improved sensitivity by injecting a photopolymerization initiator and an organic phosphate compound to the composition.
Nowadays, in a flat panel display field, a market share of a liquid crystal display (LCD) sharply increases. The LCD mainly used for an existing medium size or small size mobile display and monitor has been used for a big screen monitor and television. As a size of a screen increases, high sensitivity is requested to shorten a process time. Further, as a size of a screen increases, a brighter backlight is employed to solve brightness problem. As the backlight becomes bright, in a black matrix, a higher light shielding characteristic different from an existing light shielding characteristic is requested.
Therefore, as a content of carbon black, a pigment used in a composition to improve a light shielding characteristic, continuously increases, a process characteristic of a black matrix is continuously deteriorated and thus a process margin is lowered and many failures occur at each process stage, and thus a production yield is deteriorated.
Defects caused in each process due to the increase of the amount of carbon black used to improve a light shielding property include a defect or stain fatally occurring at a vacuum dry step (VCD process); pin stain occurring at a pre-bake step; chuck stain occurring at an exposure step; and developing stain, pattern separation, remainder, and a projection occurring at a developing step.
In the photosensitive composition industry, as an effort for reducing a processing time to increase a production yield, a process equipment is adjusted to approach a limit value and thus a standard required for a photosensitive composition is further raised.
In Korean Unexamined Patent Application Publication No. 2006-86999, in a photosensitive resin composition comprising a binder polymer, a polymerization compound having an ethylenically unsaturated bond, a photoinitiator, and a solvent, (i) at least one solvent selected from a first solvent group having a boiling point range of 140-159° C.; (ii) at least one solvent selected from a second solvent group having a boiling point range of 160-179° C.; and (iii) at least one solvent selected from a third solvent group having a boiling point range of 180-200° C., are used as a solvent, and a photosensitive resin composition in which the ratio of the first solvent: the second solvent: and the third solvent are 50-90 weight %: 10-40 weight %: 2-40 weight % is disclosed.
However, since the photosensitive resin composition disclosed in Korean Unexamined Patent Application Publication No. 2006-86999, contains the first solvent having a relatively low boiling point in a large amount of 50-90 weight % of the entire solvent, it cannot be used for a black matrix of uniform thin film having no surface defect and can only be used for a color filter. Actually, all exemplary embodiments of Korean Unexamined Patent Application Publication No. 2006-86999 describe only a composition for color filters and no example describes application to a black matrix.